PHE 3025 Assignment Threats to Validity of Research
PHE 3025 Assignment Threats to Validity of Research
Three Experimental Designs
To make things easier, the following will act as representations within particular designs:
X: Treatment
O: Observation or measurement
R: Random assignment
The three experimental designs discussed in this section are:
1) The One Shot Case Study
There is a single group and it is studied only once. A group is introduced to a treatment or condition and then observed for changes which are attributed to the treatment
X O
The problems with this design are:
A total lack of manipulation. Also, the scientific evidence is very weak in terms of making a comparison and recording contrasts.
There is also a tendency to have the fallacy of misplaced precision, where the researcher engages in tedious collection of specific detail, careful observation, testing and etc., and misinterprets this as obtaining solid research. However, a detailed data collection procedure should not be equated with a good design. In the chapter on design, measurement, and analysis, these three components are clearly distinguished from each other.
History, maturation, selection, mortality, and interaction of selection and the experimental variable are potential threats against the internal validity of this design.
2) One Group Pre-Posttest Design
This is a presentation of a pretest, followed by a treatment, and then a posttest where the difference between O1 and O2is explained by X:
O1 X O2
However, there exists threats to the validity of the above assertion:
History: between O1 and O2 many events may have occurred apart from X to produce the differences in outcomes. The longer the time lapse between O1 and O2, the more likely history becomes a threat.
Maturation: between O1 and O2 students may have grown older or internal states may have changed and therefore the differences obtained would be attributable to these changes as opposed to X. For example, if the US government does nothing to the economic depression starting from 2008 and let the crisis runs its course (this is what Mitt Romney said), ten years later the economy may still be improved. In this case, it is problematic to compare the economy in 2021 and that in 2011 to determine whether a particular policy is effective; rather, the right way is to compare the economy in 2021 with the overall (e.g. 2011 to 2021). In SPSS the default pairwise comparison is to contrast each measure with the final measure, but it may be misleading. In SAS the default contrast scheme is Deviation, in which each measure is compared to the grand mean of all measures (overall).
Testing: the effect of giving the pretest itself may effect the outcomes of the second test (i.e., IQ tests taken a second time result in 3-5 point increase than those taking it the first time). In the social sciences, it has been known that the process of measuring may change that which is being measured: the reactive effect occurs when the testing process itself leads to the change in behavior rather than it being a passive record of behavior (reactivity: we want to use non-reactive measures when possible).
Instrumentation: examples are in threats to validity above
Statistical regression: or regression toward the mean. Time-reversed control analysis and direct examination for changes in population variability are proactive counter-measures against such misinterpretations of the result. If the researcher selects a very polarized sample consisting of extremely skillful and extremely poor students, the former group might either show no improvement (ceiling effect) or decrease their scores, and the latter might appear to show some improvement. Needless to say, this result is midleading, and to correct this type of misinterpretation, researchers may want to do a time-reversed (posttest-pretest) analysis to analyze the true treatment effects. Researchers may also exclude outliers from the analysis or to adjust the scores by winsorizing the means (pushing the outliers towards the center of the distribution).
Others: History, maturation, testing, instrumentation interaction of testing and maturation, interaction of testing and the experimental variable and the interaction of selection and the experimental variable are also threats to validity for this design.
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Communication is so very important. There are multiple ways to communicate with me:
Questions to Instructor Forum: This is a great place to ask course content or assignment questions. If you have a question, there is a good chance one of your peers does as well. This is a public forum for the class.
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Important information for writing discussion questions and participation
Welcome to class
Hello class and welcome to the class and I will be your instructor for this course. This is a -week course and requires a lot of time commitment, organization, and a high level of dedication. Please use the class syllabus to guide you through all the assignments required for the course. I have also attached the classroom policies to this announcement to know your expectations for this course. Please review this document carefully and ask me any questions if you do. You could email me at any time or send me a message via the “message” icon in halo if you need to contact me. I check my email regularly, so you should get a response within 24 hours. If you have not heard from me within 24 hours and need to contact me urgently, please send a follow up text to
I strongly encourage that you do not wait until the very last minute to complete your assignments. Your assignments in weeks 4 and 5 require early planning as you would need to present a teaching plan and interview a community health provider. I advise you look at the requirements for these assignments at the beginning of the course and plan accordingly. I have posted the YouTube link that explains all the class assignments in detail. It is required that you watch this 32-minute video as the assignments from week 3 through 5 require that you follow the instructions to the letter to succeed. Failure to complete these assignments according to instructions might lead to a zero. After watching the video, please schedule a one-on-one with me to discuss your topic for your project by the second week of class. Use this link to schedule a 15-minute session. Please, call me at the time of your appointment on my number. Please note that I will NOT call you.
Please, be advised I do NOT accept any assignments by email. If you are having technical issues with uploading an assignment, contact the technical department and inform me of the issue. If you have any issues that would prevent you from getting your assignments to me by the deadline, please inform me to request a possible extension. Note that working fulltime or overtime is no excuse for late assignments. There is a 5%-point deduction for every day your assignment is late. This only applies to approved extensions. Late assignments will not be accepted.
If you think you would be needing accommodations due to any reasons, please contact the appropriate department to request accommodations.
Plagiarism is highly prohibited. Please ensure you are citing your sources correctly using APA 7th edition. All assignments including discussion posts should be formatted in APA with the appropriate spacing, font, margin, and indents. Any papers not well formatted would be returned back to you, hence, I advise you review APA formatting style. I have attached a sample paper in APA format and will also post sample discussion responses in subsequent announcements.
Your initial discussion post should be a minimum of 200 words and response posts should be a minimum of 150 words. Be advised that I grade based on quality and not necessarily the number of words you post. A minimum of TWO references should be used for your initial post. For your response post, you do not need references as personal experiences would count as response posts. If you however cite anything from the literature for your response post, it is required that you cite your reference. You should include a minimum of THREE references for papers in this course. Please note that references should be no more than 5 years old except recommended as a resource for the class. Furthermore, for each discussion board question, you need ONE initial substantive response and TWO substantive responses to either your classmates or your instructor for a total of THREE responses. There are TWO discussion questions each week, hence, you need a total minimum of SIX discussion posts for each week. I usually post a discussion question each week. You could also respond to these as it would count towards your required SIX discussion posts for the week.
I understand this is a lot of information to cover in 5 weeks, however, the Bible says in Philippians 4:13 that we can do all things through Christ that strengthens us. Even in times like this, we are encouraged by God’s word that we have that ability in us to succeed with His strength. I pray that each and every one of you receives strength for this course and life generally as we navigate through this pandemic that is shaking our world today. Relax and enjoy the course!
Hi Class,
Please read through the following information on writing a Discussion question response and participation posts.
Contact me if you have any questions.
Important information on Writing a Discussion Question
- Your response needs to be a minimum of 150 words (not including your list of references)
- There needs to be at least TWO references with ONE being a peer reviewed professional journal article.
- Include in-text citations in your response
- Do not include quotes—instead summarize and paraphrase the information
- Follow APA-7th edition
- Points will be deducted if the above is not followed
Participation –replies to your classmates or instructor
- A minimum of 6 responses per week, on at least 3 days of the week.
- Each response needs at least ONE reference with citations—best if it is a peer reviewed journal article
- Each response needs to be at least 75 words in length (does not include your list of references)
- Responses need to be substantive by bringing information to the discussion or further enhance the discussion. Responses of “I agree” or “great post” does not count for the word count.
- Follow APA 7th edition
- Points will be deducted if the above is not followed
- Remember to use and follow APA-7th edition for all weekly assignments, discussion questions, and participation points.
- Here are some helpful links
- Student paper example
- Citing Sources
- The Writing Center is a great resource